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EP-2016-048

(Submitted on 15 Mar 2016)

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Abstract

Violations of $ CPT$ symmetry and Lorentz invariance are searched for by
studying interference effects in $ B^0$ mixing and in $ B^0_s$ mixing. Samples
of $ B^0\to J/\psi K^0_{\mathrm{S}}$ and $ B^0_s\to J/\psi K^+ K^-$ decays are
recorded by the LHCb detector in proton--proton collisions at centre-of-mass
energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3
fb$^{-1}$. No periodic variations of the particle-antiparticle mass differences
are found, consistent with Lorentz invariance and $ CPT$ symmetry. Results are
expressed in terms of the Standard Model Extension parameter $\Delta a_{\mu}$
with precisions of $ \mathcal{O}(10^{-15})$ and $ \mathcal{O}(10^{-14})$ GeV
for the $ B^0$ and $ B^0_s$ systems, respectively. With no assumption on
Lorentz (non-)invariance, the $ CPT$-violating parameter $z$ in the $ B^0_s$
system is measured for the first time and found to be $ \mathcal{R}e(z) =
-0.022 \pm 0.033 \pm 0.005$ and $ \mathcal{I}m(z) = 0.004 \pm 0.011\pm 0.002$,
where the first uncertainties are statistical and the second systematic.

Figures and captions

Values of $\mathcal{R}e (z)$ obtained from fits in bins of sidereal phase for (top)
the $ B ^0$ sample and (bottom) the $ B ^0_ s $ sample. The solid line shows the
variation of $\mathcal{R}e (z)$ from the $\Delta a_{\mu}$ fits, using the average $ B $ momentum.

Periodograms for (top) the $ B ^0$ and (bottom) the $ B ^0_ s $ sample. The
insets show a zoom around the solar (red dashed line) and sidereal (blue
solid line) frequencies, which have been made by highly oversampling the
frequencies in this narrow range.

This ZIP file contains supplemetary material for the publication
LHCb-PAPER-2016-005. The files are:
supplementary.pdf : An overview of the extra figures
*.pdf, *.png, *.eps, *.C : The figures in various formats